What does a third degree heart block indicate?

• A. Impulse conduction is normal
• B. Present conduction between atria and ventricles
• C. Absence of impulse conduction between atria and ventricles
• D. Impulse conduction is less severe than second degree blocks

Answer: (C)

A third-degree heart block, also known as complete heart block, indicates a complete absence of impulse conduction between the atria and the ventricles. This means that there is no electrical communication between these two chambers of the heart, leading to them beating independently of one another. In this condition, the atria may still generate impulses, but these impulses do not get through to the ventricles, resulting in a dissociation between the heart's upper and lower chambers.

This independent activity can result in symptoms such as bradycardia or syncope, and often requires medical intervention such as the placement of a pacemaker to restore proper coordination between the atrial and ventricular contractions. Understanding this distinction is important in differentiating third-degree block from other types, such as first or second-degree blocks, where some level of conduction is still present.